Under the proposals, grammar schools will be encouraged to work with nearby primary schools to improve access for poorer pupils and be more flexible about admissions, allowing children to join or leave at 14 or 16.

May said it was “completely illogical” to make it illegal to open good schools, and accused other politicians of putting their own “dogma and ideology” before pupils, and denying others access to the kind of education that they themselves had often benefited from.

Selective schools have the ability to cater to the individual needs of every child

She said: “The principle is clear, selective schools have a part to play in helping to expand the capacity of our schools system, and they have the ability to cater to the individual needs of every child.

“So the government will make up to £50 million a year available to support the expansion of good or outstanding existing grammars.”

In a statement, the organisation said it shared the “ambition and passion for social mobility”, but warned that experts were “unanimous that an expansion of grammar schools would lead to worse outcomes for the majority of children, especially the poorest”.

“Grammar schools select only a tiny proportion of children for the best education, leaving others with a second rate choice. Even with quotas, poorer children will have a harder job of getting into these schools. And for the overwhelming majority of children who don’t get in, the evidence is clear that they get worse grades and a worse education.”

The reforms will also hit independent schools, which May said would face “tougher” requirements to qualify for charitable status.

She said such institutions were able to “reduce their tax bills by millions every year”, and said those with capacity would be required to set up free schools and sponsor institutions which are struggling.

May criticises politicians who she says would ‘deny’ to other children the type of education from which they benefited. Perhaps these politicians realise that any benefit was achieved at the expense of others.